Graphene / polymer strain sensors for structural health monitoring

  • Alizé Gaumet

Student thesis: Doctoral ThesisPhD


In this thesis, we will describe our work on two different types of graphene / polymer strain sensors aiming at initiating the research towards the full evaluation of their potential for structural health monitoring. The first type consists of a self-sensing piezoresistive graphite-polydimethylsiloxane composite film, in which conductive highly oriented pyrolitic graphite nanoparticles are embedded in an insulating polydimethylsiloxane matrix, whose electromechanical properties have already been well-established. The second type consists in self-assembled graphene-naphthalene diimide-graphene tunnelling multilayer devices that have so far only been fabricated on rigid and opaque SiO2/Si substrate.

We fabricated miniature graphite-polydimethylsiloxane composite strain sensors and embedded them in various construction materials and set-ups, including in relatively realistic settings, and subjected them to a variety of testing techniques in order to study their strain sensing abilities in a civil engineering context. We demonstrated their micro-cracking detection abilities in different cementitious materials by resolving the local strain in-situ. We also demonstrated the ability of these sensors to detect strain redistribution from one direction to another, which together with incomplete strain relaxation within the composite, appeared to affect their response to dynamic strain applied through cyclic uniaxial compression loading. In addition to these findings, our graphite-polydimethylsiloxane composite strain sensors were also demonstrated to have greatly consistent strain sensing abilities and are highly sensitive to strain, low-cost, reproducible, scalable down to hundreds of nanometres, industrially scalable, biocompatible, as well as suitable for the fabrication of large-scale arrays. The above attributes qualify our composite strain sensors as a promising alternative to conventional strain gauges employed in structural health monitoring.

We kick-started the research into the fabrication of graphene-naphthalene diimide-graphene tunnelling multilayer devices on flexible and transparent PEN substrate with the aim of advancing the fields of structural health monitoring, wearable devices and artificial skins. These devices are indeed miniature, extremely light-weight, transparent, can be manufactured in very large numbers in the form of an array and are expected to be piezoresistive with a very high strain sensitivity allowed by the width of their tunnelling barrier varying under the application of strain. We carried out a relatively thorough study of the fabrication of the multilayer devices on flexible and transparent polyethylene naphthalate substrate through a process using a combination of wet and dry graphene transfer approaches from industrially manufactured monolayer graphene sheets on copper substrate as starting samples. An excellent yield very close to 100 % was achieved for the production of monolayer graphene electrodes on polyethylene naphthalate substrate. A good alignment of the top and bottom monolayer graphene electrodes into a cross formation was reached, though a better reproducibility is called upon.

An undesired loss in conductivity for half of the electrodes during the assembly of the tunelling multilayer devices was, however, observed. In this thesis, we give possible causes for this loss in conductivity, as well as general guidance as to how it could be resolved.
Date of Award18 Jan 2023
Original languageEnglish
Awarding Institution
  • University of Bath
SupervisorAlain Nogaret (Supervisor), Dan Pantos (Supervisor) & Richard Ball (Supervisor)

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